diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6f4324e4..2d7633a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,11 +13,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- Preserve dict key order in the output of `tree_unflatten`, `tree_map`, and `tree_map_with_path` by [@XuehaiPan](https://github.com/XuehaiPan) in [#46](https://github.com/metaopt/optree/pull/46).
+-
 
 ### Changed
 
-- Change keyword argument `initializer` back to `initial` for `tree_reduce` to align with `functools.reduce` C implementation by [@XuehaiPan](https://github.com/XuehaiPan) in [#47](https://github.com/metaopt/optree/pull/47).
+-
 
 ### Fixed
 
@@ -29,6 +29,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ------
 
+## [0.9.0] - 2023-03-23
+
+### Added
+
+- Preserve dict key order in the output of `tree_unflatten`, `tree_map`, and `tree_map_with_path` by [@XuehaiPan](https://github.com/XuehaiPan) in [#46](https://github.com/metaopt/optree/pull/46).
+
+### Changed
+
+- Change keyword argument `initializer` back to `initial` for `tree_reduce` to align with `functools.reduce` C implementation by [@XuehaiPan](https://github.com/XuehaiPan) in [#47](https://github.com/metaopt/optree/pull/47).
+
+------
+
 ## [0.8.0] - 2023-03-14
 
 ### Added
@@ -185,7 +197,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ------
 
-[Unreleased]: https://github.com/metaopt/optree/compare/v0.8.0...HEAD
+[Unreleased]: https://github.com/metaopt/optree/compare/v0.9.0...HEAD
+[0.9.0]: https://github.com/metaopt/optree/compare/v0.8.0...v0.9.0
 [0.8.0]: https://github.com/metaopt/optree/compare/v0.7.0...v0.8.0
 [0.7.0]: https://github.com/metaopt/optree/compare/v0.6.0...v0.7.0
 [0.6.0]: https://github.com/metaopt/optree/compare/v0.5.1...v0.6.0
diff --git a/README.md b/README.md
index 9dd2369b..3a3b651b 100644
--- a/README.md
+++ b/README.md
@@ -496,7 +496,7 @@ False
 ([3, 1, 2], PyTreeSpec(OrderedDict([('b', [*]), ('a', [*, *])])))
 ```
 
-Since OpTree v0.9.0, the key order of the reconstructed output dictionaries from `tree_unflatten` is guaranteed to be consistent with the key order of the input dictionaries in `tree_flatten`.
+**Since OpTree v0.9.0, the key order of the reconstructed output dictionaries from `tree_unflatten` is guaranteed to be consistent with the key order of the input dictionaries in `tree_flatten`.**
 
 ```python
 >>> leaves, treespec = optree.tree_flatten({'b': [3], 'a': [1, 2]})
@@ -525,7 +525,7 @@ This property is also preserved during serialization/deserialization.
 
 > Note that there are no restrictions on the `dict` to require the keys are comparable (sortable).
 > There can be multiple types of keys in the dictionary.
-> The keys are sorted in ascending order by `key=lambda k: k` first if capable otherwise fallback to `key=lambda k: (k.__class__.__qualname__, k)`. This handles most cases.
+> The keys are sorted in ascending order by `key=lambda k: k` first if capable otherwise fallback to `key=lambda k: (f'{k.__class__.__module__}.{k.__class__.__qualname__}', k)`. This handles most cases.
 >
 > ```python
 > >>> sorted({1: 2, 1.5: 1}.keys())
@@ -534,7 +534,7 @@ This property is also preserved during serialization/deserialization.
 > Traceback (most recent call last):
 >     ...
 > TypeError: '<' not supported between instances of 'int' and 'str'
-> >>> sorted({'a': 3, 1: 2, 1.5: 1}.keys(), key=lambda k: (k.__class__.__qualname__, k))
+> >>> sorted({'a': 3, 1: 2, 1.5: 1}.keys(), key=lambda k: (f'{k.__class__.__module__}.{k.__class__.__qualname__}', k))
 > [1.5, 1, 'a']
 > ```
 
diff --git a/optree/version.py b/optree/version.py
index 499c6389..1dd19d2d 100644
--- a/optree/version.py
+++ b/optree/version.py
@@ -14,7 +14,7 @@
 # ==============================================================================
 """OpTree: Optimized PyTree Utilities."""
 
-__version__ = '0.8.0'
+__version__ = '0.9.0'
 __license__ = 'Apache License, Version 2.0'
 __author__ = 'OpTree Contributors'
 __release__ = False